This invention relates to the treatment of metal surfaces to increase their resistance to corrosion. It further relates to compositions which form a corrosion-resistant film on metal surfaces to which they are applied. In one aspect, the invention relates to the treatment of downhole metal surfaces of oil and gas wells to inhibit corrosion of the metal surfaces.
The problem of corrosion of metal surfaces in contact with air and water is well known. Corrosion and pitting are accelerated in environments in which metal surfaces are in contact with water having a high electrolyte concentration and with naturally-occurring chemicals such as hydrogen sulfide, carbon dioxide and organic acids. such environments are typical of downhole conditions in oil and gas wells, in which corrosion of metal pipes, pumps and other equipment poses a serious problem requiring monitoring of well sites, frequent maintenance and costly replacement of parts. Oil recovery operations in deep-sea fields present these corrosion problems in their most extreme form. These downhole metal surfaces are in contact with large volumes of corrosive chemicals such as dissolved acid gases present in the recovered oil, and, in addition, the metal surfaces are subjected to temperatures of 250.degree. F. or higher and pressures of 3000 psig or greater, the extreme conditions of temperature and pressure acting to accelerate corrosion and to intensify the problems of identifying effective corrosion inhibitors and applying and maintaining chemical protection for the equipment. In offshore oil wells, secondary recovery operations involving water-flooding of undersea formations subject downhole equipment to highly corrosive sea water containing dissolved oxygen.
Conventional corrosion-inhibiting agents are often not effective at all under such extreme conditions or reduce corrosion significantly for only a short period of time and then must be reapplied, often at great expense and inconvenience if the well site is not easily accessible or, as in the case of off-shore wells, poses difficulties of transporting and applying large volumes of chemicals.
It is therefore an object of this invention to provide a composition which can be applied to a metal surface to inhibit corrosion and pitting on the metal. It is a further object to provide a method of treating metal surfaces so as to form a film which inhibits corrosion on the metal even under extreme conditions of temperature and pressure and in highly corrosive environments. It is a further object of the invention to provide an article having a surface film of a composition which inhibits corrosion.